Tag Archives: study

There was a glowing article in theatlanticcities.com with the tantalyzying headline Dedicated Bike Lanes Can Cut Cycling Injuries in Half, referring to this study, published in a peer-reviewed, albeit public health and not a transportation, journal:

The design of the study is intriguing: it’s based on randomly choosing a “control site” along the participant’s (i.e. the crash victim) route.

Cycle Tracks are NINE TIMES safer?

Undoubtedly, the incredibly safety differential of “cycle tracks” will be the main take-away. The study found them to be NINE TIMES safer compared to their reference street (essentially a “worst case”: a mulitlaned arterial with on-street parking and no bicycle facilities whatsoever). The actual result is OR 0.11 (0.02, 0.54) — that is to say Odds Ratio of 11 percent, with a 95% confidence interval between 2 and 54%, compared to the reference road.

Ok, so I don’t understand a lot about statistics, but the wide range between the lower and upper confidence interval (27X) is a clue. In short there is not very much/many cycle tracks in the study, mentioned only as “despite their (cycle track’s) low prevalence in Toronto and Vancouver”. There were two reported collisions, and 10 control sites on cycle tracks (out of N=648). In the critique of the study by John Forester he found during the study period there was apparently only one cycle track, the Burrard Street bridge, in both cities — my that is a “low prevalence” — here is his take-away:

In the much more impressive cycle-track issue, the authors proclaimed enormous crash reduction without informing the readers of the two relevant facts. First, that their data came from only one installation. Second, that that installation was not along a typical city street but in the only situation in which a plain cycle track could possibly be safe, a place without crossing or turning movements by motorists, cyclists, or pedestrians…

And even regarding the Burrard Street Bridge cycle-track, the timeline seems to conflict/overlap somewhat with the study dates. According to a surprisingly detailed account on wiki a test of what sounds to be the cycle-track was “to begin in June 2009. The proposed trial began on July 13. It saw the southbound motor-vehicle curb lane and the northbound-side sidewalk allocated to bicycles, with the southbound-side sidewalk allocated to pedestrians. The reassigned lane was separated from motor vehicles by a physical barrier” The timeline of the study was for bicyclist injuries presenting to the ERs “between May 18, 2008 and November 30, 2009″.

But wait? According to this (from mid-2011, i think, the date is unclear), Tesche said there are other cycle tracks: “However, we were able to examine separated bike lanes elsewhere in the city, including Burrard Bridge, Carrall Street, and other locations that met our definition: that is, a paved path alongside city streets that’s separated from traffic by a physical barrier,” Teschke told councillors.

Some Other Things i Noticed

The highest median observed motor vehicle speed along major roads was 44kph (27mph)! This is comically low compared to what I am used to here in Phoenix. Intersting trivia answer: 27.79mph — the fastest time on record for a person running.

One-third of the incidents involved collisions with MVs. The balance were various types of falls or collisions with objects. The one-third number is pretty close to the 26% reported by another ER-based survey of bicyclist injuries ( Injuries to Pedestrians and Bicyclists: An Analysis Based on Hospital Emergency Department Data. linked here ); though this isn’t directly comparable, e.g. in the former case, mountain biking was not eligible for the the study, whereas in the latter it was any sort of injury incurred on a bike.

There was a bunch of interesting data collected in the survey (which the author’s are nice enough to give a link to) that are not in the final study. I’m not sure why. I would have been interested to see various spins on lightness/darkness vs. cyclist’s light usage.

The Injury Prevention Article

and here’s another similar article, or perhaps pretty much the same(?):

NYC Protected Bike Lanes on 8th and 9th Avenue in Manhatten

According to a report (it’s really a brochure) by NYC DOT cited by americabikes.org; these are the “First protected bicycle lane in the US: 8th and 9th Avenues (Manhattan)”…”35% decrease in injuries to all street users (8th Ave) 58% decrease in injuries to all street users (9th Ave) Up to 49% increase in retail sales (Locally-based businesses on 9th Ave from 23rd to 31st Sts., compared to 3% borough-wide)”. I don’t know if or what the data are to back up these claims. I also don’t know much about how these are structured, what was done with signals, how long these are, or how long they have been in place… here is a google street view at 9th/23rd. (these segments show up in Lusk’s May 2013 AJPH article, discussed below)

Methodology aside, though the study claims an increase in safety, it found only a modest increase: “RR [relative risk] of injury on cycle tracks was 0.72 (95% CI 0.60 to 0.85) compared with bicycling in reference streets”. I.e. a 28% reduction in crashes.

More Lusk, July 2013 Article in AJPH

Oh, it’s like it never ends:

Bicycle Guidelines and Crash Rates on Cycle Tracks in the United States
Anne C. Lusk, PhD, Patrick Morency, MD, PhD, Luis F. Miranda-Moreno, PhD, Walter C. Willett, MD, DrPH, and Jack T. Dennerlein, PhD Published online ahead of print May 16, 2013; it was in the July printed edition of American Journal of Public Health. “For the 19 US cycle tracks we examined, the overall crash rate was 2.3 … per 1 million bicycle kilometers… Our results show that the risk of bicycle–vehicle crashes is lower on US cycle tracks than published crashes rates on roadways”. What are published rates? Later they say “published crash rates per million bicycle kilometers range
from 3.75 to 54 in the United States”. The first number is footnoted to Pucher/Irresistible (which is discussed and linked here), and the second to, if you can believe it, a study of Boston bicycle messengers (Dennerlein, 2002. I haven’t bothered to look that one up). In Pucher, it’s in Fig 10 where they quote US injuries at 37.5 per 10 million km for the period 2004-2005, sourced to US Department of Transportation (2007), which is/are Traffic Safety Fact Sheets according to the footnotes. Pucher does, um, mention that injury rates comparisons across countries are particularly suspect; Figure 10 would lead on to believe the UK and US have similar fatality rates, whereas US injury rates are quoted as SEVEN TIMES higher. (Pucher’s claim/point is that NL and DK are very safe, while US and UK are very dangerous). In any event TSF does not list injury rates per unit of travel, only number of injuries, e.g. TSF 2005 quotes 45,000 injuries (these are presumably some sort of statistical estimate?). To get the rate estimates, he uses one of the surveys (household trans survey?).

Paul Schimek gathered data on the 19 cycletracks listed in table 3; he added another column “intersections per km” and sorted them into two groups, 1) Urban Side Paths and 2) Side Paths with Minimal Crossflow. And as would be predicted by traffic engineering principles, the former had very high (7.02) versus the latter which had very low (0.57) crashes per 1 Million bicycle kilometers. The published letter-the-editor of AJPH is available in full on pubmed (or draft version on google docs) which is well worth reading. He, by the way, provides an estimate for whole US bike crashes at 3.5 per 1M bike km’s; which fits rather nicely between the high/low cycletrack numbers. The bottom line is that the AASHTO guidelines (which prohibit the on-street barriers; but permit bicycle paths adjacent to the roadway where there is “minimal cross flow by motor vehicles”) , contrary to Lusk’s assertions, are well-founded. This blog post at bicycledriving.org also discusses the same AJPH article, with links to both Schimek’s published letter, and Lusk’s published response. This is wrapped up in an article the Paul wrote A Review of the Evidence on Cycle Track Safety, Paul was kind enough to send me draft copy dated October 10, 2014.

Oh, and here is John Forester’s review of Lusk’s May AJPH article. In summary, Forester says “This review does not evaluate Lusk’s method of calculating car-bike collision rates. However, the cycle tracks with high collision rates are all in high-traffic areas with high volumes of crossing and turning traffic, while the cycle tracks with low collision rates are all in areas with low volumes of turning and crossing traffic. That is what should be expected, but it says nothing about any reduction in collisions that might have been caused by the introduction of cycle tracks. The data of this study provide no evidence that cycle tracks reduce car bike collisions”.

What about Davis, CA?

The article/thesis paper Fifty Years of Bicycle Policy in Davis, CA 2007
Theodore J. Buehler has a deep history. Davis, home of course to UC Davis, installed and compared designs including what we would now call a cycle track, (emphasis added):

Lane location relative to motorized traffic
The early experiments included three different types of bike facilities (see examples at the top of this section):

bike lanes between car lanes and the parking lane (Third St.),

bike lanes between the parking lane and the curb (Sycamore Lane), [what we now call a cycle track, or protected bike lane]and

bike paths adjacent to the street, between the curb and the sidewalk (Villanova Ave.).

… The on-road lanes worked best, the behind-parking lanes were the worst, and the adjacent paths were found to work in certain circumstances.

Notations from the City of Davis website says (retrieved 1/19/2017. Emphasis added):

Sycamore Lane Experiment: This 1967 bike lane used concrete bumpers to separate parked cars from the bike only lane. The parked cars screened the visibility of bicyclists coming into intersections and cars would unknowingly drive into the bike lane. This bike lane design was eventually abandoned.
The 1967 separated bike lanes on Sycamore Lane didn’t prevent conflicts with turning vehicles. Today at this intersection there are special bike-only traffic signals that provide cyclists their own crossing phase. These innovative bicycle signals were the first of their kind to be installed in the United States.

Other Critiques

2012 Teschke: Route Infrastructure and the Risk of Injuries to Bicyclists: A Case-Crossover Study
Selection bias: uses comparison streets instead of a before-after situation; study claims greatly increased safety on cycle tracks, but the cycle tracks chosen for the study were not representative of a typical cycle track, in that all were on roads with limited or nonexistent road intersections. It is not surprising that bicycle facilities that have little or no possibility of interaction with motor vehicles are safer than those that have many such possibilities, and if all bicycle tracks were completely separated from turning and crossing traffic, they would indeed be safer than cycling on the road. The problem is, cycle tracks with few road intersections are very rare indeed.

2011 Lusk: Risk of Injury for Bicycling on Cycle Tracks Versus in the Street (Montreal, Canada)
The infamous Lusk study. Selection bias: study claims increased safety on bicycle specific infrastructure, but its street comparisons are flawed – the streets compared were in no way similar other than their general geographic location. Busy downtown streets with multiple distractions per block were twinned with bicycle tracks on quieter roads with fewer intersections and fewer distractions..